Einstein held that imagination is more important than knowledge: “Knowledge is limited. Imagination encircles the world.”

I define imagination as the faculty of the mind that forms and manipulates images, propositions, concepts, emotions, and sensations above and beyond, and sometimes independently of, incoming stimuli, to open up the realms of the abstract, the figurative, the possible, the hypothetical, and the universal.

Imagination comes in many forms and by many degrees, ranging from scientific reasoning to musical appreciation, and overlaps with a number of other cognitive constructs including belief, desire, emotion, memory, supposition, and fantasy. Belief, like perception, aims at according with reality, while desire aims at altering reality. Emotion also aims at according with reality, but more particularly at reflecting the significance of its object, or class of object, for the subject—an aspect that it shares with many forms of imagination. Like imagination, memory can involve remote imagery. But unlike imagination, it is rooted in reality and serves primarily to frame belief and guide action. Memories are often more vivid than imaginings, which are, in turn, more vivid than suppositions. Suppositions tend to be cold and cognitive, and lacking in the emotional and existential dimensions of imagination. Finally, fantasy may be understood as a subtype of imagination, namely, imagination for the improbable.

I say the improbable rather than the impossible, because there is a theory that, just as perception justifies beliefs about actuality, so imagination justifies beliefs about possibility (or at least, metaphysical as opposed to natural possibility). To quote Hume, ‘It is an established maxim in metaphysics, that whatever the mind clearly conceives, includes the idea of possible existence, or in other words, that nothing we imagine is absolutely impossible.’ Could ghosts, the devil, time travel etc. really be possible? I think inconceivability may be a better guide to impossibility than conceivability to possibility. But what does it mean for something to be conceivable or inconceivable, and by whom?

It has to be said that, until very recently, most human societies did not mark a strict divide between imagination and belief, or fiction and reality, with each one informing and enriching the other. In fact, it could be argued that, in many important respects, the fiction primed over the reality—and even that this has been, and perhaps still is, one of the hallmarks of our species. Today, there are pills for people who confuse imaginings and beliefs, but back then no one ever thought that life, with its much harder hardships, might be meaningless—which I think tells us quite a bit about imagination and its uses, and also about mental illness.

The uses of imagination are many, more than I can enumerate. Most children begin to develop pretend play at around 15 months of age. What are children doing when they pretend play? And why are they so absorbed in works of imagination? When I was seven years old, I would devour book after book, and plead with my parents for those not already on the shelves. By playing out scenarios and stretching themselves beyond their limited experience, children seek to make sense of the world and to find their place within it. This meaning-making is joyful and exciting, and has an echo in every act of creation.

When we look at the Mona Lisa, we see much more than just the brushstrokes. In fact, we barely see the brushstrokes at all. In imagination as in our dreams, we ascribe form, pattern, and significance to things, and then reflect them back onto those things. Without this work of interpreting and assimilating, the world would be no more than an endless stream of sense impressions, as it might sometimes seem to those who lack imagination, with no hope of escape or reprieve.

More than that, by imagination we are able to complete the world, or our world, by conjuring up the missing parts, and even to inhabit entirely other worlds such as Middle-earth or the Seven Kingdoms. Imagination remains highly active throughout adulthood, and what is chick lit or even pornography if not an aid to the adult imagination? In one year (2017), Pornhub recorded 28.5 billion visits, equivalent to about four times the world population—and that’s just on the one site.

If imagination enables us to feel at home in the world, it also enables us to do things in the world. Science progresses by hypothesis, which is a product of imagination, and philosophy makes frequent use of thought experiments such as the brain in the vat, the trolley problem, and up to Plato’s Republic. Imagination makes knowledge applicable by forming associations and connections. It opens up possibilities, and guides decision-making by playing out those possibilities. So many of our failures, and some of our successes, are in fact failures of the imagination.

Imagination also enables us to talk to one another, understand one another, and work together. Without it, there could be no metaphor, no irony, no humor, no past or future tense, and no conditional. Indeed, there could be no language at all, for what are words if not symbols and representations? By imagination, we can put ourselves in other people’s shoes, think what they think, and feel what they feel. Problems in autism, which can be interpreted as a disorder of imagination, include abnormalities in patterns of communication, impairments in social interactions, and a restricted repertoire of behaviors, interests, and activities.

I’m lucky to have received a decent education, but one thing it didn’t do is cultivate my imagination. In recent years, I’ve been trying to recover the bright and vivid imagination that I left behind in childhood.

I’ve been doing just three things, all of them very simple—or, at least, very simple to explain.

• Being aware of the importance of imagination.
• Making time for sleep and idleness.
• Taking inspiration from nature.

I’ll conclude with these few words from William Blake, which hint at the significance of the natural world and the transcending power of imagination,

The tree which moves some to tears of joy is in the eyes of others only a green thing that stands in the way. Some see nature all ridicule and deformity… and some scarce see nature at all. But to the eyes of the man of imagination, nature is imagination itself.